Rotor assemblies for vehicle alternators typically include a pair of pole pieces, a coil wire held in a region formed between the pole pieces, a rotor shaft, a pair of stamped metal fans and a slip ring assembly. The slip ring assembly and the pole pieces are mounted on the rotor shaft assembly and the metal fans are attached to outboard faces on the pole pieces.
The slip ring assembly generally includes a hub to support the slip rings and a pair of terminals. The terminals extend across the face of a pole piece to connect the slip rings to respective free ends of the coil wire. Accordingly, as the terminals and one of the fans are positioned adjacent that outboard face, the terminals and the fan must be configured to accommodate one another.
In the event a molded fan is molded to the outboard face of the pole piece, the terminals must be adapted to cooperate with the mold forming the molded fan. In particular, the terminals ideally pass from the slip rings through the molded fan to reach the ends of the coil wire. The slip rings and rotor shaft should be kept free of mold material so that the slip rings have electrically conductive surfaces and so that bearings may be mounted on the rotor shaft to allow the rotor assembly to rotate relative a stator and alternator housing of the vehicle alternator.
Accordingly, it is desirable to have a slip ring assembly which mates with the mold forming the molded fan and which also serves as a mold shutoff device between the mold and the pole piece to which the fan is to be molded. Molten mold material is injected into the mold at high temperatures and at high pressures. Therefore, to form a proper seal between the mold, the slip ring assembly and the pole piece, mating or sealing surfaces on these components must be held firmly in contact. This is accomplished by placing a large compressive load across the mold, the slip ring assembly and the rotor assembly which is to be molded.
Prior art slip ring assemblies are not well suited to mate between a mold and a pole piece to form an effective seal. Further, prior art slip ring assemblies typically cannot withstand large compressive loads being placed thereacross.
The present invention includes a slip ring assembly that overcomes these shortcomings of previous slip ring assemblies.